Medicine is about saving lives and in this endeavor, the cutting edge focus is on the actions and resources available to emergency responders in life threatening situations and first aid medics is war zones. In Iraq, improvements in injury management, including better designed tourniquets and hemostat bandages, have significantly reduced fatalities. Rapid access to fresh whole blood and recombinant activated Factor VII also has reduced the likelihood that severely wounded combatants bled to death.
Bleeding or hemorrhaging is the loss of blood from the circulatory system. Bleeding can occur internally from blood vessels in organs inside the body. Alternatively, bleeding can occur externally through a disruption of the vasculature which could be concealed resulting in a hematoma, ore in the skin. Desanguination is a massive loss of blood from the body and results in acute blood loss anemia. The primary risk of desanguination is a reduction in the number of erythrocytes carrying hemoglobin and oxygen to the cells of the body. Typically, 100 mL of blood transports approximately 20 mL of oxygen. Various organs extract the amount of oxygen they require for normal functioning from the blood circulating through the organ. For example, the kidney, brain and heart extract approximately 2, 6.5 and 10.5 mL of oxygen per 100 mL of blood in circulation. When a person losses more than 20% of the total blood volume a lack of oxygen to the cells or hypoxia can occur. Hypoxia causes all blood vessels to dilate, speeding up the blood flow. The venus blood return to the heart increases, and as a result the heart works harder and faster trying to prevent cardiopulmonary congestion. Severe shock and lactic acidosis can result. Ultimately, if blood loss exceeds 40% to 50% of plasma volume, the resulting desanguination can lead to heart and circulatory failure and death. Initially, the body compensates for a rapid reduction in oxygen supply by extracting liquids and electrolytes from tissues and interstitial spaces to expand the volume of plasma and formation of new blood cells. This decreases the viscosity of blood which increases the risks of cardiac dilation, heart valve insufficiency and ventricular dysfunction. Severe bleeding can also reduce the amount of iron in the body to the extent that the bone marrow is unable to compensate for the loss of red blood cells. Bone marrow repletion of the blood supply takes significant time (weeks) which would not be relevant in an acute blood loss scenario likely to occur in a post traumatic setting.